This section provides background information related to the present disclosure which is not necessarily prior art. With reference to FIG. 1, current vehicles may employ one or more heat exchangers 2, 4, such as radiator 2 and condenser 4, to cool liquids that are continuously circulated through heat generating devices on the vehicle. Regarding a radiator 2, liquid coolant may first be passed through an internal combustion engine before the coolant is circulated through radiator 2 to be cooled. Similarly, a vehicle air-conditioning system may compress a refrigerant that is then cooled by being passed through condenser 4. Airflow 6 and a fan 8 may assist in delivering air through each of radiator 2 and condenser 4. A shroud 10 may further assist in directing airflow. However, such an arrangement may be subject to improvement. For instance, when heated liquids are introduced into a heat exchanger, thermal strain may develop at specific locations of the heat exchanger. Area 12 depicts an area of radiator 2 that is blocked by airflow 6 and thus may experience thermal strain. Thermal strain occurs during expansion and contraction created during heating and cooling of the material that forms the rigid and connected coolant channels of heat exchanger 2. The rate at which heating and cooling occurs depends upon the temperature, flow rate and quantity of heat of incoming liquid supplied into and through material of heat exchanger 2 relative to the temperature and rate of change of the temperature of material of the heat exchanger at the location at which the incoming liquid is received.
FIG. 2 depicts a cross-flow heat exchanger 16 that exhibits thermal strain within a material of heat exchanger 16. More specifically, a liquid 18 flows into inlet 14 and horizontally across a bottom portion 20 of heat exchanger 16 before flowing into a top portion 22 of heat exchanger 16 and out outlet 17. Liquid 18 flow transitions from flowing horizontally across bottom portion 20 to top portion 22 at header tank 26. Because liquid 18 cools while passing across and through a bottom portion 20 and also while passing across a top portion 22, thermal strain may occur at the juncture or adjacent portions of bottom portion 20 and top portion 22. As an example, at area 28 is a location that experiences simultaneous contact with the highest temperature of liquid 18 and the lowest temperature of liquid 24. FIG. 2 also graphically presents a representative heat differential within heat exchanger 16. With mean temperature increasing from left to right on temperature distribution graph 30, one may see that the mean temperature 32 of liquid 18 in bottom portion 20 is higher than the mean temperature 34 of liquid 24 in top portion 22. Thus, across a juncture of lower portion 20 and upper portion 22, such as at area 28, greatest expansion and contraction of the material of heat exchanger 16 may occur. Such a heat differential may cause cracks and hasten leaks from heat exchanger 16. What is needed then is a structure and method for controlling thermal strain on a heat exchanger.